In recent years, larger display devices have been required. For example, television sets including display panels with a diagonal of greater than or equal to 40 inches have spread in ordinary households and have taken on an aspect of an increase in size. In addition, digital signage and a public information display (PID) are given. Larger digital signage, PID, and the like can provide the increased amount of information, and attract more attention particularly when used for advertisement or the like, so that the effectiveness of the advertisement can be increased.
Display devices are expected to find widespread application and modes of the display devices become diversified.
Examples of the display device include, typically, a liquid crystal display device, a light-emitting device including a light-emitting element such as an organic electroluminescent (EL) element or a light-emitting diode (LED), and an electronic paper performing display by an electrophoretic method or the like.
For example, in a basic structure of an organic EL element, a layer containing a light-emitting organic compound is provided between a pair of electrodes. By voltage application to this element, the light-emitting organic compound can emit light. A display device including such an organic EL element needs no backlight which is necessary for liquid crystal display devices and the like; therefore, thin, lightweight, high contrast, and low power consumption display devices can be obtained.
Patent Document 1 discloses a flexible active matrix light-emitting device in which an organic EL element and a transistor serving as a switching element are provided over a film substrate.